To identify genetic risk factors for childhood-onset affective disorders. We plan to identify genes that contribute to the development of childhood- onset depression using a strategy that combines affected relative pairs (ARP) and association studies that employ family based controls which we call haplotype relative risk (HRR) methods. The research plan is to collect DNA from childhood-onset unipolar depression probands, their parents, and their affected relatives. DNA will be extracted from blood or buccal mucosa taken from the probands, affected relatives, parents and when available, from connecting family members in the pedigree. DNA's will be typed from the ARP sample and the HRR sample for evaluation of candidate genes. Probands and parents will be screened for the presence of expanded trinucleotide repeats as some evidence for genetic anticipation has been documented for affective disorders.